The present invention relates to a magnetoresistance effect device, a magnetic head, a magnetic head assembly, and a magnetic recording/reproducing system. More precisely, it relates to a magnetoresistance effect device, a magnetic head, a magnetic head assembly, and a magnetic recording/reproducing system, in which is used a giant magnetoresistance effect element having high sensitivity and high reliability.
The recent tendency in the art is toward small-sized, large-capacity magnetic recording media, for which there are increasing great expectations of high-power MR heads (magnetoresistance effect heads). For the MR film which is the basic constituent element in those MR heads, widely noticed is a spin valve film having a multi-layered magnetic film with a sandwich structure of magnetic layer/nonmagnetic layer/magnetic layer, in which one magnetic layer is pinned for its magnetization owing to the magnetic coupling bias applied thereto (this layer may be referred to as a xe2x80x9cpinned magnetic layerxe2x80x9d or xe2x80x9cpinned layerxe2x80x9d) while the other magnetic layer is reversed for its magnetization owing to the applied magnetic field (this layer may be referred to as a xe2x80x9cfree magnetic layerxe2x80x9d or xe2x80x9cfree layerxe2x80x9d). The spin valve film of that type produces a giant magnetoresistance effect (GMR) through the relative angle change in the magnetization direction between those two magnetic layers.
As other types of MR films, known are an anisotropic magnetoresistance effect film (AMR film) made of an NiFe alloy or the like, an artificial lattice film, etc. Though smaller than that in an artificial lattice film, the MR ratio in a spin valve film is at least 4% and is much larger than that in an AMR film. A spin valve film can saturate its magnetization even in a low magnetic field, and is therefore suitable to MR heads. MR heads incorporating such a spin valve film receive much expectations for their practical applications. Specifically, for increasing the recording density in magnetic recording on magnetic discs and the like, high-sensitivity GMR heads (giant magnetoresistance effect heads) are indispensable.
Early GMR heads incorporate, in its GMR device, a spin valve film that comprises a free layer, a nonmagnetic spacer layer, a pinned magnetic layer and an antiferromagnetic layer. In those, the increase in the sensitivity of the film is indispensable for increasing the recording density through reduction in the recording track width. However, if the free layer is thinned so as to increase the sensitivity of the film for that purpose, the stray magnetic field from the pinned magnetic layer will shift the bias point. In that case, it is often difficult to effectively correct the thus-shifted operating point by the current magnetic field.
On the other hand, a so-called laminated pinned ferromagnetic layer (hereinafter referred to as xe2x80x9cSyAFxe2x80x9d, or xe2x80x9cSynthetic AFxe2x80x9d) has been proposed (U.S. Pat. No. 5,465,185), which comprises two ferromagnetic layers as antiferromagnetically coupled via an antiferromagnetically coupling layer existing therebetween. In principle, the antiferromagnetically coupled, pinned layer of that type would produce very small stray magnetic field, thereby readily ensuring the operating point.
One case of a spin valve film with SyAF is referred to, in which one of the two ferromagnetic layers adjacent to the nonmagnetic spacer layer is a ferromagnetic layer A while the other adjacent to the antiferromagnetic layer is a ferromagnetic layer B and in which the ferromagnetic layer A and the ferromagnetic layer B have the same magnetic thickness, thickness x saturation magnetization. In that case, the stray magnetic fields from the layer A and layer B cancel each other so that there is substantially no stray magnetic field generated by the pinned layer. As a result, the pinned layer of that type is no more susceptible to a magnetic field and has the significant advantage of stable pinned magnetization at around the blocking temperature, Tb, at which the magnetic coupling bias of the antiferromagnetic layer is lost.
The problem with the present technology, that an object of the present invention is to resolve, is that the inventors found, the bias point designing in an applied sense current is difficult, especially in device using thin free layer so as to increase the sensitivity of output signal for high density recording.
In a first aspect, the present invention provide a magnetoresistance effect element that attains the object mentioned above comprising a nonmagnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer as separated by the nonmagnetic spacer layer, in which the first ferromagnetic layer has a magnetization direction different from the magnetization direction of the second ferromagnetic layer when the applied magnetic field is zero, and the second ferromagnetic layer comprises a pair of ferromagnetic films as antiferromagnetically coupled to each other and a coupling film that separates the pair of ferromagnetic films while antiferromagnetically coupling them, and a nonmagnetic high-conductivity layer adjacent to the first ferromagnetic layer on the plane opposite to the plane at which the first ferromagnetic layer is contacted with the nonmagnetic spacer layer.
In the present invention, the magnetoresistance effect device may realize extremely high sensitivity while maintaining a good bias point. Preferably, the MR device may be in the form of a so-called spin valve device (see U.S. Pat. No. 5,206,590), in which the first ferromagnetic layer is not coupled to the second ferromagnetic layer and the magnetization directions of the two layers are perpendicular to each other at zero applied magnetic field. Preferably, the applied magnetic field to change the magnetization of the first ferromagnetic layer may be smaller than that to change the magnetization of the second ferromagnetic layer, and the magnetization of the second ferromagnetic layer is pinned to such a degree that the magnetization direction may not change even in the presence of an applied magnetic field.
In the present invention, the nonmagnetic high-conductivity layer may contain an element of which the specific resistance in bulk at room temperature is not larger than 10 xcexcxcexa9cm, thereby realizing good characteristic, namely, high MR ratio owing to the spin filter effect in the ultra-thin first ferromagnetic layer and low Hcu.
For high density recording and for realizing the increase in MR ratio owing to the spin filter effect of the nonmagnetic high-conductivity layer, the thickness of the first ferromagnetic layer may be between 0.5 nanometers and 4.5 nanometers.
In the present invention, the thickness of the nonmagnetic high-conductivity layer and that of the second ferromagnetic layer may be so designed that the wave asymmetry, (V1xe2x88x92V2)/(V1+V2) , in which V1 indicates the peak value of the reproduction output in a positive signal field and V2 indicates the peak value of the reproduction output in a negative signal field, may fall between minus 0.1 and plus 0.1.
In the present invention, the MR device may satisfy the conditions of 0.5 nanometersxe2x89xa6tm(pin1)xe2x88x92tm(pin2)+t(HCL)xe2x89xa64 nanometers and t(HCL)xe2x89xa70.5 nanometers, in which t(HCL) indicates the thickness of the nonmagnetic high-conductivity layer (in terms of the Cu layer having a specific resistance of 10 xcexcxcexa9cm), and tm(pin1) and tm(pin2) indicate the magnetic thicknesses of the pair of ferromagnetic films, respectively, in the second ferromagnetic layer in terms of saturation magnetization of 1 Tesla, where pin 1 is of one of the ferromagnetic films disposed adjacent to the nonmagnetic spacer layer and pin2 is of another one of the ferromagnetic films. Satisfying the conditions noted above, the MR device may realize the wave asymmetry falling between minus 0.1 and plus 0.1 and high MR.
In the present invention, the first ferromagnetic layer may have a magnetic thickness, thicknessxc3x97saturation magnetization, of smaller than 4.5 nanometer Tesla.
In the present invention, the nonmagnetic high-conductivity layer may be of a metal film that contains at least one metal element selected from the group consisting of copper (Cu), gold (Au), silver (Ag), ruthenium (Ru), iridium (Ir), rhenium (Re), rhodium (Rh), platinum (Pt), palladium (Pd), aluminium (Al), osmium (Os) and nickel (Ni), all of which are advantageous for meeting the condition of realizing low Hin.
In the present invention, the nonmagnetic high-conductivity layer may have a laminate film composed of at least two layers, for attaining low Hin and soft magnetic characteristics control. In the present invention, in the laminate film, the layer adjacent to the first ferromagnetic layer may contain copper (Cu) which is especially suitable for realizing high MR ratio, low Hcu and soft magnetic characteristics. In the laminate film, the layer not adjacent to the first ferromagnetic layer may contain at least one element selected from the group consisting of ruthenium (Ru), rhenium (Re), rhodium (Rh), palladium (Pd), platinum (Pt), iridium (Ir) and osmium (Os) all of which are especially suitable for realizing low Hin, low Hcu and soft magnetic characteristics control.
In the present invention, the nonmagnetic high-conductivity layer may have a thickness of from 0.5 nanometers to 5 nanometers and the element may realize low Hcu and high MR ratio.
In the present invention, the layer that is contacted with the nonmagnetic high-conductivity layer at the plane opposite to the plane at which the nonmagnetic high-conductivity layer is contacted with the first ferromagnetic layer may contain at least one element selected from the group consisting of tantalum (Ta), titanium (Ti), zirconium (Zr), tungsten (W), hafnium (Hf), molybdenum (Mo), and chromium (Cr), and the device may realize low Hin and high MR ratio.
In the present invention, the first ferromagnetic layer may be of a laminate film that comprises an alloy layer containing nickel iron (NiFe) and a layer containing cobalt (Co) and the device may realize high MR ratio and soft magnetic characteristics.
In the present invention, the first ferromagnetic layer may be an alloy layer containing cobalt iron (CoFe) and the element may realize high MR ratio and soft magnetic characteristics.
In the present invention, for pinning the magnetization direction of the second ferromagnetic layer, an antiferromagnetic layer may be laminated over the layer.
In the present invention, for realizing still high MR ratio even after thermal treatment in its production, the antiferromagnetic layer may be made of a material, XzMn1-z in which x indicates at least one element selected from the group consisting of iridium (Ir), ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd) and rhenium (Re) and the compositional factor z falls between 5 atm. % and 40 atm. %, in the present invention.
In the present invention, the antiferromagnetic layer may be made of a material, XzMn1-z in which X indicates at least one element selected from the group consisting of platinum (Pt) and palladium (Pd) and the compositional factor z falls between 40 atm. % and 65 atm. %, and the element may maintain high MR ratio.
In the present invention, the nonmagnetic spacer may be of a metal layer containing copper (Cu) and its thickness may be between 1.5 nanometers and 2.5 nanometers and the element may realize high MR ratio for more efficiently utilizing the effect of high MR ratio by the nonmagnetic high-conductivity layer, and may also realize low Hcu.
In the present invention, the pair of ferromagnetic films as antiferromagnetically coupled to each other may have the same thickness and the difference in the magnetic thickness, thicknessxc3x97saturation magnetization, between the pair of ferromagnetic films may fall between 0 nanometer Tesla and 3 nanometer Tesla, and the element may realize high MR, improved ESD resistance, and the thermal stability of the second ferromagnetic layer.
In the present invention, the antiferromagnetically layer coupling the pair of ferromagnetic films to each other may comprise Ru and its thickness may fall between 0.8 nanometers and 1.2 nanometers.
In a second aspect, the present invention provides a magnetoresistance effect device comprising a nonmagnetic spacer layer, a first ferromagnetic layer and a second ferromagnetic layer as separated by the nonmagnetic spacer layer, in which the magnetization direction of the first ferromagnetic layer differs from that of the second ferromagnetic layer when the applied magnetic field is zero, and a nonmagnetic high-conductivity layer adjacent to the first ferromagnetic layer on the plane opposite to the plane at which the first ferromagnetic layer is contacted with the nonmagnetic spacer layer, in which the thickness of the nonmagnetic high-conductivity layer and the thickness of the ferromagnetic layer are so designed that the wave asymmetry, (V1xe2x88x92V2)/(V1+V2), in which V1 indicates the peak value of the reproduction output in a positive signal field and V2 indicates the peak value of the reproduction output in a negative signal field, falls between minus 0.1 and plus 0.1.
For attaining the wave asymmetry of falling between minus 0.1 and plus 0.1, it may not be always necessary to employ the constitution of SyAF in the device but also a single layer. In that case, it is desirable that the second ferromagnetic layer of a single layer may have a magnetic thickness of from 0.5 nanometer Tesla to 3.6 nanometer Tesla. If the magnetic thickness of the single layer of the second ferromagnetic layer is larger than 3.6 nanometer Tesla, it may be difficult to attain the wave asymmetry noted above. On the other hand, if it is smaller than 0.5 nanometer Tesla, the MR ratio in the device will be noticeably small.
In a third aspect, the present invention provides a magnetoresistance effect device comprising a nonmagnetic spacerlayer, first and second ferromagnetic layers separated by the nonmagnetic spacer layer, in which the magnetization direction of the first ferromagnetic layer differs from that of the second ferromagnetic layer when the applied magnetic field is zero, and a nonmagnetic high-conductivity layer adjacent to the first ferromagnetic layer on the plane opposite to the plane at which the first ferromagnetic layer is contacted with the nonmagnetic spacer layer and that the device satisfies the conditions of 0.5 nanometersxe2x89xa6tm(pin)+t(HCL)xe2x89xa64 nanometers and t(HCL)xe2x89xa70.5 nanometers, in which t(HCL) indicates the thickness of the nonmagnetic high-conductivity layer in terms of copper having a specific resistance of 10 xcexcxcexa9cm, and tm(pin) indicates the magnetic thicknesses of the second ferromagnetic layer, respectively, in the second ferromagnetic layer in terms of saturation magnetization of 1Tesla.
Satisfying the conditions noted above, the MR device may realize the wave asymmetry falling between minus 0.1 and plus 0.1 and high MR, even when the second ferromagnetic layer therein is a single layer.
In a fourth aspect, the present invention provides a magnetoresistance effect device comprising a pinned magnetic layer and a free layer as separated by a nonmagnetic spacer layer disposed therebetween, and an antiferromagnetic layer as laminated on the pinned magnetic layer for pinning the magnetization of the pinned magnetic layer, the pinned magnetic layer comprises a pair of ferromagnetic layers, a ferromagnetic layer A as disposed adjacent to the nonmagnetic spacer layer and a ferromagnetic layer B as disposed adjacent to the antiferromagnetic layer, that those ferromagnetic layers A and B are antiferromagnetically coupled to each other via an antiferromagnetically coupling layer existing therebetween, and that the close-packed plane of the antiferromagnetic layer is so oriented that the half-value width of the diffraction peak from the closed packed plane of the layer in its rocking curve appears at 8xc2x0 or smaller.
In a fifth aspect, the present invention provides a magnetoresistance effect element comprising a nonmagnetic spacer layer, and first and second ferromagnetic layers separated by the nonmagnetic spacer layer, a magnetization direction of the first ferromagnetic layer being at an angle relative to a magnetization direction of the second ferromagnetic layer at zero applied magnetic field, the second ferromagnetic layer comprising first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films for coupling the first and second ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field, the magnetization of the first ferromagnetic layer freely rotating in signal magnetic field. The element further comprises a pair of electrodes coupled to the magnetoresistance effect film and having respective inner edges; and a pair of longitudinal biasing layers for providing bias magnetic fields to the first ferromagnetic layer in parallel with a longitudinal direction of the first ferromagnetic layer and having respective inner edges, wherein the inner edges of the pair of electrodes are disposed between the inner edges of the pair of longitudinal biasing layers.
In a sixth aspect, the present invention provides a magnetoresistance effect device comprising a spin valve film and a pair of electrodes for supplying sense current to the spin valve film, in which the spin valve film comprises at least one nonmagnetic spacer layer and at least two magnetic layers as separated by the nonmagnetic spacer layer existing therebetween. The spin valve film is provided with a magnetoresistance effect-improving layer of being a laminate film of a plurality of metal films as disposed adjacent to the magnetic layer on the plane opposite to the plane at which the nonmagnetic spacer layer is contacted with the magnetic layer, and with a nonmagnetic layer acting as a underlayer or a protecting layer as disposed adjacent to the magnetoresistance effect-improving layer on the plane opposite to the plane at which the magnetic layer is contacted with the magnetoresistance effect-improving layer, and that the element essentially constituting the metal film of the magnetoresistance effect-improving layer that is adjacent to the magnetic layer does not form a solid solution with the element essentially constituting the magnetic layer.
In the above described element, the magnetoresistance effect-improving layer may exhibit, as its one capability as follows. In the device in which the free layer is thin, the magnetoresistance effect-improving layer acts as a nonmagnetic high-conductivity layer such as that mentioned above. In this, the interface between the ultra-thin free layer and the nonmagnetic high-conductivity layer is formed of a combination of materials not producing a solid solution therein, thereby preventing any diffusive scattering of electrons in the interface so as to improve the up-spin transmittance. With that constitution, the device maintains high MR ratio therein. As not having a solid solution phase, the interface is stable to thermal treatment and does not cause the reduction in MR ratio in the device. The magnetoresistance effect-improving layer exhibits its ability to improve the magnetoresistance effect of the device, while being based not only on its spin filter capability but also on its additional capabilities to control the microcrystal structure of the spin valve film and to reduce the magnetostriction in the film.
In one specific example, the magnetic layer adjacent to the magnetoresistance effect-improving layer may be made of Co or a Co alloy, the magnetoresistance effect-improving layer may comprise at least one element selected from Cu, Au and Ag. In another example of the device where the magnetic layer adjacent to the magnetoresistance effect-improving layer may be made of an Ni alloy, the magnetoresistance effect-improving layer may comprise at least one element selected from Ru, Ag, Cu, and Au. In the device, the magnetoresistance effect-improving layer may comprise any one or more elements of Cu, Au, Ag, Pt, Rh, Ru, Al, Ti, Zn, Hf, Pd, Ir, etc.
The magnetoresistance effect device of the invention is based on the technique of reducing the magnetostriction in the CoFe alloys and others noted above by or Au/Cu laminate film, Ru/Cu laminate film, or Auxe2x80x94Cu alloys. Specifically, the device comprises a spin valve film and a pair of electrodes for supplying sense current to the spin valve film, in which the spin valve film comprises one nonmagnetic spacer layer and two magnetic layers as separated by the nonmagnetic spacer layer existing therebetween, and this is characterized in that, of at least two magnetic layers, one of which the magnetization direction varies, depending on the applied magnetic field, is oriented to fcc(111), and that the d(111) lattice spacing is between 0.2055 and 0.2035 nanometers.
In a seventh aspect, the present invention provides a magnetoresistance effect device comprising a giant magnetoresistance effect film and a pair of electrodes for supplying current to the giant magnetoresistance effect film, in which the giant magnetoresistance effect film comprises at least a pair of a pinned magnetic layer and a free layer as separated by a nonmagnetic spacer layer disposed therebetween, and an antiferromagnetic layer as laminated on the pinned magnetic layer for pinning the magnetization of the pinned magnetic layer, and which is characterized in that the pinned magnetic layer comprises a pair of ferromagnetic layers, a ferromagnetic layer A as disposed adjacent to the nonmagnetic spacer layer and a ferromagnetic layer B as disposed adjacent to the antiferromagnetic layer, that those ferromagnetic layers A and B are antiferromagnetically coupled to each other via an antiferromagnetically coupling layer existing therebetween, and that the antiferromagnetic layer has a thickness of at most 20 nanometers and has a magnetic coupling coefficient, J, for the ferromagnetic layer B of at least 0.02 erg/cm2 at 200xc2x0 C.
In an eighth aspect, the present invention provides a magnetoresistance effect element comprising a giant magnetoresistance effect film and a pair of electrodes for supplying current to the giant magnetoresistance effect film, in which the giant magnetoresistance effect film comprises at least a pair of a pinned magnetic layer and a free layer as separated by a nonmagnetic spacer layer disposed therebetween, and an antiferromagnetic layer as laminated on the pinned magnetic layer for pinning the magnetization of the pinned magnetic layer, the pinned magnetic layer comprises a pair of ferromagnetic layers, a ferromagnetic layer A as disposed adjacent to the nonmagnetic spacer layer and a ferromagnetic layer B as disposed adjacent to the antiferromagnetic layer, those ferromagnetic layers A and B are antiferromagnetically coupled to each other via an antiferromagnetically coupling layer existing therebetween, and the antiferromagnetic layer has a thickness of at most 20 nanometers and contains at least any one of ZxMn1xe2x88x92x (where Z is at least one selected from Ir, Rh, Ru, Pt, Pd, Co and Ni, and 0 less than x less than 0.4), ZxMn1xe2x88x92x (where Z is at least one selected from Pt, Pd and Ni, and 0.4xe2x89xa6xxe2x89xa60.7), or ZxCr1xe2x88x92x (where Z is at least one selected from Mn, Al, Pt, Pd, Cu, Au, Ag, Rh, Ir and Ru, and 0 less than x less than 1).
The magnetic head and the magnetic recording/reproducing system of the invention incorporate the magnetoresistance effect device of the invention noted above. Specifically, the magnetic head of the invention is characterized by comprising a lower magnetic shield layer, a magnetoresistance effect device of the invention such as that noted above, which is formed on the lower magnetic shield layer via a lower reproducing magnetic gap therebetween, and an upper magnetic shield layer as formed on the magnetoresistance effect device via an upper reproducing magnetic gap therebetween.
The magnetic head for separated recording/reproducing of the invention is provided with a reproducing head that comprises a lower magnetic shield layer, a magnetoresistance she effect device of the invention such as that noted above, which is formed on the lower magnetic shield layer via a lower reproducing magnetic gap therebetween, and an upper magnetic shield layer as formed on the magnetoresistance effect device via an upper reproducing magnetic gap therebetween, and with a recording head that comprises a lower magnetic pole which is common to the upper magnetic shield layer, a recording magnetic gap as formed on the lower magnetic pole, and an upper magnetic pole as formed on the recording magnetic gap.
The magnetic head assembly of the invention is characterized by comprising a head slider having the separated recording/reproducing magnetic head of the invention noted above, and an arm having a suspension on which the head slider is mounted. The magnetic recording/reproducing system of the invention is characterized by comprising a magnetic recording medium, and a head slider provided with the separated recording/reproducing magnetic head of the invention noted above with which signals are written on the magnetic recording medium in a magnetic field and signals are read in the magnetic field as generated by the magnetic recording medium.
The magnetoresistance effect device of the invention mentioned above is applicable not only to magnetoresistance effect heads but also to magnetoresistance effect sensors.
Any one of the present invention may be provided not only in disc drive system but also other magnetic storage system, such as magnetic memory device. The magnetic disc drive system of the invention is characterized in that a current is applied to the magnetoresistance effect device in the magnetoresistance effect head to generate a magnetic field and that the system is provided with a mechanism capable of pinning the magnetization of the pinned magnetic layer in a predetermined direction in the thus-generated magnetic field.
Method for producing the magnetoresistance effect elements of the invention comprises heating the pair of ferromagnetic film A and the ferromagnetic film B of the synthetic pinned layer in a magnetic field, after the film of the giant magnetoresistance effect device has been formed but before it is patterned, thereby pinning the magnetization of the pinned magnetic layer in a predetermined direction.